Name _____________________________________ Pd ____ Date _______________________
Blood Spatter Lab
Part 1: Height & Velocity of Blood Drop - In this lab we will use graphing techniques to analyze the effect of the
blood drop height and velocity on the shape and diameter of the blood spatter.
Procedure:
1. Place a piece of scrap copy paper on the floor.
2. Drop a single drop of blood straight down onto the scrap paper from a height of 20 cm.
3. Beside the drop write the height from which the blood was dropped.
4. Repeat step 2 and 3, using a different scrap copy paper, 4 more times.
5. When the parent drop is dry, use a metric ruler to measure its diameter and record it in Data Table 1.
6. Observe if splines and satellite drops were formed and record your observations in Data Table 2.
7. Repeat steps 2 through 6 on the 5 pieces of scrap copy paper, each time raising the dropper an additional 20
cm to a maximum of 180 cm.
8. Clean up your area and put the materials away.
9. Calculate the average diameter for each height and record the values in the data table.
10. Create a chart (graph) that displays height on the x-axis and spatter diameter on the y-axis.
Data Table 1 – Effect of Drop Height on Parent Drop Diameter
Parent Drop Diameter (cm)
HEIGHT (cm)
Trial 1
Trial 2
Trial 3
Trial 4
Trial 5
Average
20
40
60
80
100
120
140
160
180
Data Table 2 – Effect of Drop Height on Formation of Splines and Satellite Drops
Formation of Splines and Satellite Drops (yes/no)
Trial 1
Trial 2
Trial 3
Trial 4
HEIGHT
(cm)
Splines Satellite Splines Satellite Splines Satellite Splines Satellite
20
40
60
80
100
120
140
160
180
Trial 5
Splines Satellite
Conclusions
1. Describe the relationship between the distance of the fall (height) and the diameter of the parent drop.
2. What is the relationship between the distance of the fall (height) and the formation of splines and satellite
drops?
3. Is there height above which the diameter of the parent drop remains the same? If so, what is that height?
4. If you answered yes to #3, why do you think the drop diameter remains the same?
Part 2: Effect of Surface Type - In this lab we will investigate how the type of surface affects the shape and
diameter of the blood spatter.
Procedure:
1. Place a piece of newspaper on the floor.
2. Drop a single drop of blood straight down onto the scrap paper from a height of 60 cm.
3. Repeat step 2, 4 more times using the same surface.
4. When the parent drop is dry, use a metric ruler to measure its diameter and record it in Data Table 3.
5. Observe if splines and satellite drops were formed and record your observations in Data Table 4.
6. Repeat steps 2 through 5, using a whiteboard as the surface.
7. Clean up your area and put the materials away.
8. Calculate the average diameter for each height and record the values in the data table. Transfer your 60 cm
data from Table 1 and Table 2 to Tables 3 and 4.
Data Table 3 – Effect of Surface on Parent Drop Diameter
Parent Drop Diameter (cm)
Surface
Trial 1
Trial 2
Trial 3
Trial 4
Trial 5
Average
Copy Paper
Newspaper
Whiteboard
Data Table 4 – Effect of Surface on Formation of Splines and Satellite Drops
Formation of Splines and Satellite Drops (yes/no)
Trial 1
Trial 2
Trial 3
Trial 4
Surface Splines Satellite Splines Satellite Splines Satellite Splines Satellite
Copy
Paper
Newspaper
Whiteboard
Conclusions
5. Which surface produced the largest diameter drop?
6. Which surface produced the smallest diameter drop?
7. Which surface produced the most splines and satellite drops?
8. Which surface produced the fewest splines and satellite drops?
9. Why did the type of surface affect the drop size and splatter pattern?
Trial 5
Splines Satellite
Part 3: Motion of Victim – You will investigate how motion affects the size and shape of the droplets and splines.
Procedure:
1. Tape a long piece of paper (4-5 meters in length) to the floor.
2. Hold the dropper upside down so that your hand is out and away from your body (waist level), but is still over
the paper.
3. Start off walking at a SLOW WALKING RATE along the paper strip from one end to the other and GENTLY
squeeze the dropper as you walk so that blood is released one drop at a time. Be sure that all the drops land
on your paper strip. Missed the paper? Use a paper towel to wipe it off the floor!
4. Repeat steps 2 and 3 using a NORMAL WALKING RATE and a FAST WALKING RATE.
5. Draw a sketch of the drops showing their shape for each walking speed in Data Table 5 below.
6. Measure the size of the drops and the distance between them at each speed and record in Data Table 6.
7. Clean up your area and put away your materials.
Data Table 5 – Effect of Victim’s Motion on Blood Spatter Patterns
Walking Rate
Sketch of Blood Spatter Pattern
Slow
Normal
Fast
Data Table 6 – Effect of Victim’s Motion on the Size and Distance between Drops
Walking Rate
Drop Width (cm)
Drop Length (cm)
Distance Between Drops (cm)
Slow
Normal
Fast
Conclusions
10. What did you notice about the shape of the drops as you increased your walking speed?
11. What did you notice about the spines as you increased your walking speed?
12. What did you notice about the size of the drops as you increased your walking speed?
13. What did you notice about the distance between the drops as you increased your walking speed?
Part 4: Angle of Impact – You will be investigate the drop patterns created by blood landing at different angles
from the same height.
Procedure:
drop height
1. Label five pieces of copy paper with your names and
50 cm
then indicate the angle for each drop - 15o, 30o, 45o,
board
60o, or 75o.
2. Tape the first piece of paper on the board and align
the clipboard with the 15o mark on the protractor.
Hold the bottle of blood at a height of 50 cm from
protractor
the top of the table.
3. GENTLY squeeze the dropper so that ONE drop of
blood is released and lands on the paper. Repeat
two more times at this angle.
4. Continue testing by dropping blood from a height of 50 cm at each of the other angles.
5. When drops are dry measure the width and length of the parent drops and record the information in Data
Table 7. Do not include the tail of the drop in your length measurements.
6. Clean up your area and put away your materials.
Data Table 7 – Effect of Angle of Impact on Dimensions of Blood Spatter
Angle of Impact
15°
30°
45°
60°
75°
Trial 1
Length, cm
Width, cm
Trial 2
Length, cm
Width, cm
Average
Trial 3
Length, cm
Width, cm
Length, cm
Width, cm
Conclusions
14. What happened to the size and shape of the parent drop as the angle of impact decreased?
15. How can investigators estimate the angle of impact from the size and shape of the parent drop?
Part 5: Medium-Velocity Blood Spatter – You will simulate blunt force trauma and calculate the effect on blood
spatter patterns.
Procedure:
1. Place sponge on smashing surface within the white-wall confines.
2. Measure and record the height from the ground to the original placement of the sponge. This is the zcoordinate value.
3. Smash the sponge causing it to spatter.
4. Locate three individual spatter drops and label them A, B and C.
5. String from Spatter A to the original placement of the sponge.
6. Measure and record the angle between the smashing surface and the string. This is the Measured Angle of
Impact (AOI).
7. Repeat steps 6 & 7 for Drop B and Drop C.
8. Measure and record both the length and the width (for Drops A-C). This is the Length and Width.
9. Use the following steps to calculate the Angle of Impact for each of Drops A-C.
a. Divide the width of the drop by the length of the drop.
b. On your calculator, press “Shift” or “Second”, then press “Sin”, then type in your answer to part (a). Press
“enter”.
c. Record this value in the table.
Data Table 8 – Effect of Velocity on Blood Spatter
Drop A
Drop B
Drop C
Measured AOI, degrees
Length of drop, cm
Width of drop, cm
Calculated AOI, degrees
z-coordinate, cm
Conclusions:
16. Why did we cover the blood in sponge?
17. If the diameter of a spatter drop is large, what does that tell you about the velocity of the blood at impact?
18. If the distance from the source origin and the spatter is large, what does that tell you about the velocity of the
blood at impact?
19. Theoretically, the Measured AOI and the Calculate AOI should be the same. If they don't match explain some
possible errors: